The bowling ball which is in popular use in this country is of a weight not to exceed 16 pounds and of an outside diameter of approximately 8.550 to 8.595 inches. The ball is drilled to provide a grip for the bowler. A two (2) hole or three (3) hole grip is generally used. A two (2) hole grip accommodates the thumb and middle finger of the bowler. A three (3) hole grip accommodates the thumb, ring finger and middle finger of the bowler. In a three (3) hole grip, the holes for the ring finger and middle finger may either be drilled shallow (i.e., to the first knuckle) to provide a fingertip grip or deep (i.e., to the second knuckle) to provide a conventional grip. Alternately, grips for which the fingers are inserted to intermediate positions between the first and second knuckle are referred to as semi-fingertip grips. The drilling of holes in the ball, of necessity, removes material from the ball and accounts for unbalanced conditions in what would otherwise be a homogenous ball.
Various methods and apparatus have been proposed in the prior art to compensate for the weight removed by drilling finger and thumb holes. Traditionally, a form of weight block has been incorporated into the design of prior art bowling balls. It has been generally thought that the center of gravity of the ball should be slightly off the geometric center during manufacture of the ball so that after drilling the finger and thumb holes, the ball will be reasonably balanced. To date, the balance of a bowling ball has been measured generally by means of a beam balance scale. Therefore, the balance explored is necessarily a static phenomenon. Little attention has been directed at the dynamic balance properties of bowling balls.
A bowling ball that is not dynamically balanced will, among other things, wobble as it is rolled down a lane. Evidence of wobble behavior can be seen in the flared nature of the resulting ball track on the exterior surface of the ball. Wobble behavior can also be observed by a trained individual standing at the foul line or on carefully obtained high speed films.
A wobble condition due to dynamic imbalance in the ball produces numerous variables which affect the ability of the bowler to consistently use the ball to obtain high scores. Bowling with a consistently high degree of scoring requires accurate placement of the ball in the strike zone. When a spare is desired, a high degree of accuracy is required in order to knock over a pin or, in some cases, achieve a desired degree of pin action in order to knock over a number of standing pins. Dynamic imbalance in the ball impedes the ability of the bowler to control his game.
There is a large number of variables in the game of bowling some of which are under the control of the bowler and some of which are out of the bowler's control. Variables within the control of the bowler include the form utilized by the bowler to throw the ball, the grip and delivery of the bowler, the equipment selected by the bowler including the ball and shoes, and the ability of the bowler to place the ball at an intended target. Variable factors encountered by the bowler over which he has little or no control include the conditions of the lane including the surface finish, the oil coating on the lane surface, the interaction of the ball with the lane surface and the interaction of the ball with the pins after striking the pins. The ability of a bowler to compensate for lane conditions is important. Thus, the ability to accurately control movement of the ball under various conditions can result in improved or higher scores.
It is a general object of this invention to provide a bowling ball which includes weight blocks having desired properties and which are so positioned relative to the finger holes and thumb hole that the ball will exhibit a stable trajectory as it rolls and slides down the lane.